Nanoscale device could enable efficient on chip optical interconnects

A nanoscale device that converts optical signals into surface plasmon polaritons has been developed by a research team led by the Harvard School of Engineering and Applied Sciences (SEAS).

According to the team, the breakthrough will allow light to be manipulated without affecting a signal that could carry data. If implemented, it could enable on chip optical interconnects.

"If you want to send a data signal around on a tiny chip with lots of components, then you need to be able to precisely control where it's going," said Balthasar Müller, a graduate student at SEAS. "If you don't control it well, information will be lost – directivity is such an important factor."

Previously, surface plasmon polaritons have been controlled by adjusting the angle at which light strikes the surface of the coupler. However, with the new approach, light only needs to be normal to the device's surface. The polarisation of the incoming light wave – such as linear, left hand circular or right hand circular – is detected and then routed. The device can split a light beam and send parts of it in different directions, allowing for information transmission on multiple channels.

The coupler consists of a thin sheet of gold perforated in a herringbone pattern. "The solution, until now, has been a series of parallel grooves known as a grating, which does the trick but loses a large portion of the signal in the process," said Professor Federico Capasso. "[Our structure] makes it possible to control the direction of signals in a very simple and elegant way."